Tuesday, March 22, 2011

Whiskey Wednesday: Whiskey, Age and Oxygen Part 2

Two years ago, I started a little experiment to discern how oxidation impacts whiskey in an open bottle. The query I was addressing was the age old question of how long your whiskey will last once you crack open the bottle. As I said in that post:

Answering this question is harder than you might think and there are different schools of thought. Once you uncork the seal and pour a glass, you let oxygen into the whiskey bottle so oxidation is a possibility. Just how long such oxidation takes and under what circumstances is not clear.

It is common lore among whiskey fans that once a bottle is half full or less, you should drink it within 18 months to prevent oxidation and a change in flavor. Others, however, swear that whiskey can last for years at a low level and have virtually no ill effects.

So, to test this out, on December 30, 2008, I opened a new bottle of Longmorn 16 and poured it into three mini bottles. One I filled to the top such that virtually no air was left in the bottle, a second I filled approximately half way, and a third I filled to about a quarter of the way full (see picture above).

These bottles have been quietly sitting in my closet for the past two years and two months, and now it has come time to find the results of our experiment. I poured an equal measure of each whiskey into tasting glasses.

I started by tasting the whiskey from the full bottle, just to gauge my taste. This bottle had minimal oxygen exposure so it becomes the control. Part of the reason I chose Longmorn 16 for this experiment is that it's fairly subtle in flavor profile; it isn't strongly peated or sherried, flavors which can cover up many flaws. It is lightly sherried, and its general character is malty and grassy.

Now to the half bottle. The nose and flavor were pretty much identical to the full bottle. I found no discernible difference between the full bottle and the half full bottle.

And finally, the quarter fill. The nose on the quarter fill was much lighter and less forceful than on the others. While the same notes were there, they were much harder to pick up. Upon tasting it, the flavor of the quarter filled bottle was much weaker than the other two. It was lighter in character, and some of the stronger and sweeter notes had dulled, giving way to a base (as opposed to acid) type of taste. Overall, while there were certainly traces of the same flavor notes, there was a lack of dimension and complexity and a general dulling of flavor in the quarter filled bottle compared to the other malts.

I have to say that I am surprised as I had always been skeptical of the theory that whiskey would deteriorate in the bottle over two years, but this one certainly had. I don't want to overstate the deterioration. It was still plenty drinkable, but as I noted, it lacked the sharpness of flavor found in the fuller bottles.

To conclude, it seems that somewhere between a half bottle and a quarter bottle there is a point at which deterioration takes place. While it would take more exacting experimentation to find that precise point (which may well vary based on all sorts of factors), I think it's safe to say that the results of this experiment support the general thesis that it is a good idea not to let a bottle that is much less than half full languish in the cupboard for a two year period.

I guess it's time for me to start draining some of those low fill bottles in the closet.

16 comments:

Once again, another extremely thought provoking post. And I applaud the great lengths you've gone to prove it - this is the kind of stuff I love about sites like yours. For the greater good!

Anyway, I have this conversation with folks all the time and I've always been a firm believer in whiskey losing character. The way I've described it is like what happens to fruit left to over ripen on a kitchen counter (a fridge is probably more appropriate) and begin deteriorating. It becomes sweeter, it loses structure in the mouth, and all of the sharpness and bite is dulled increasingly the longer it sits in the half filled or less bottle. In short it loses what you might call its complexity and character.

If I open a bottle I try to drink it within 3-4 months. When it gets about 1/3 full I funnel it into 4oz and/or 2oz Boston Round bottles with screw caps. I label it and date the day I re-bottled it. I've found this helps immensely in keeping the whiskey on point and true to character.

One thing worth noting to the opposite of this subject. I review whiskeys and do tasting and I never review the first pour of whiskey from a bottle. I simply enjoy it because most times for me, the whiskey is like a bull in a china shop. All that alcohol just rushing to get out. In my experience it is at it's fullest and spiciest at that moment. But there's only one first pour for a consumer to have. So for me I find that 2nd -4th is the best time to really understand what that whiskey is all about. Pure theory, but it's one I'm repeatedly reminded of with each fresh bottle.

Thanks for the great comments Jason. Interesting point about not reviewing the first pour. I've noticed that difference as well, and sometimes I don't even review on the first day because I think there is sometimes a noticeable change when you wait 24 hours after opening the bottle, but that could just be perception.

Thanks for the great post, Sku. I'd been waiting for this one for a while now. I've got a Banff that I had a pour off of and absolutely loved, but had actually kind of been paralyzed on having more because I kind of dreaded the loss of character since it's such a sublime treat. This definitely gives me some comfort and looks like the Boston Rounds will be on order soon. Likewise I'll probably be enjoying it a bit more.

On the other hand - I too don't like to really render judgement on newly opened bottles. I've had them really be one thing (usually, as Jason notes, way too brash) and then find them to be an entirely different beast in the following days. Not that my reviews are worth much but I've definitely found myself holding off until things are maybe mid-shoulder - I have a few impressions of it; the occasional palate contamination is gone, and I am more sure if that random strange note I detected is really there or not.

James, just for the record, after my review, the Scotch Noob contacted me and specifically asked for the Loch Dhu. Of course, I was happy to comply since I certainly wasn't going to drink the whole thing. I threw in the Ardbeg because I thought it was too sad to just give him Loch Dhu.

I appreciate your scientific attitude! One thing I would note though, when I drink a bottle to half full it usually isn't all at once. I do it in intervals so the whisky gets more than a half full refresh. It gets refreshed a lot more, actually. That could account for why the half full obttle didn't seem aired out yet. You didn't give the vapors a chance to move into that air and then escape a few times, you only let it go once. Great job, though!

I do not think it is an effect on oxidation. I get similar effect if I pour whiskey in the glass and I leave it for half a day on a counter - lighter and less forceful.I think going from full size bottle to a mini makes a huge difference in the test. That 1/4 full mini probably did not have as much alcohol left in it as the other one due to alcohol evaporation which accounts for lighter taste and less burn. Alcohol evaporates quicker than water.

Great test. Thank you. While very informational it still leaves me wondering how how it translates to this happening with 750ml's. Exactly the same? Magnified? A half full 750ml will have more air in the bottle and have higher exposure.

Jeff, it's a good question, and not being a scientist (or at all science minded), I can't tell you. Of course, while there is more air in the 750, the proportion of air to whiskey would be the same as in the minis, so the exposure level shouldn't be any different.

Great Post and method. I did a similar test, but with 750 ml bottles around a year ago with very similar results.

The alcohol comment by Jeff is an interesting one. I imagine the impact of the change in alcohol percentage is minimal compared to the impact of oxidation, largely because I have noticed changes in flavor and sharpness greater than that of adding a few drops of water to lower the proof. Maybe next time I do an experiment I'll have to get out my hydrometer and whip my college chemistry back into shape...

But, for me, it begs the question - are there any whiskies that you think would improve from exposure to oxygen/aging/air in the bottle? Sometimes, I'm sure, we've noticed the improvement (at least in the nose) of a whisky as it sits out or "opens up". Are there any whiskies which could be improved from letting some of the edges dull and round out a little? To me, it seems possible, though my observations of long sitting half-empty bottles are not that they are improved.